1. CompSci 6 Introduction to Computer Science November 8, 2011 Prof. Rodger

2. Announcements No reading or RQ Assignment 5 due Thursday New APT out Thursday – one APT Practice Test problems out – will go over on Tues. Nov 15 Prof. Rodger no office hours this week Today –Finish example from last time –More on sort options –Regular Expressions

3. More on sort Import operator –fruit = [(“pear”,5),(“apple”,9)] fruit = sorted(fruit) fruit.sort() OR fruit = sorted(fruit) –arguments key=itemgetter(0) reverse=True

4. Regular Expressions Part of the compiler process –Can write a regular expression for each type of word in a programming language –Example Key words – if, else, elif, while Integers – 456, 78, 2, -56 Float – 3.14, 7856.2345 String – ‘word’, “this is a phrase” Special symbols – [ ] + %

5. Regular Expressions a- a a* - a repeated 0 or more times a+ - a repeated 1 or more times a? – a 0 or 1 time, so a is optional ^ - match at the beginning of the string $ - match at the end of the string. – matches anything [abc] – match a, b, or c [a-z] – match any character from a to z [^a] – match any character but a

6. More on regular expressions | - or \b - word boundary \s - whitespace character \d – match any digit When using backslashes – must use r in front of string

7. Regular expressions with re import re re.sub() – substitute re.compile() – create a pattern re.findall() See examples